Product Description

TWPro 125mm Twin Wall Insulated 15 Degree Bend – Matt Black

Model: 37-125-033

Create a gentle change of direction in a 125mm insulated chimney with the TWPro 15 Degree Twin Wall Bend. This fixed two-segment bend moves the chimney route by 15° while keeping it close to vertical.

Installers can use one bend for a small directional change or combine two matching bends with a straight pipe to create an offset. Therefore, the component provides a practical way to avoid joists, roof timbers and other obstacles without introducing a sharp change in direction.

The bend features a 316L stainless-steel inner casing, high-density mineral wool insulation and a matt-black 304-grade stainless-steel outer casing. In addition, its push-fit joint and locking band connect securely to compatible TWPro components.

Product at a Glance

• 125mm nominal internal flue diameter
• Fixed 15° chimney bend
• Two-segment construction
• Creates a gentle change in chimney direction
• Use two matching bends to form an offset
• Helps keep the chimney route close to vertical
• Suitable for internal and external chimney systems
• 316L stainless-steel inner casing
• 304-grade stainless-steel outer casing
• High-temperature matt-black external coating
• 25mm high-density mineral wool insulation
• Push-fit FitSystem connection
• Uses a locking band to secure the joint
• Suitable for compatible solid-fuel, gas and oil appliances
• HETAS approved and CE marked
• T600 temperature classification
• G50 soot-fire resistance classification
• 50mm declared distance to combustible materials
• Product model: 37-125-033

What Is a 15 Degree Twin Wall Bend Used For?

A chimney should rise as straight and vertically as possible. However, a joist, roof timber, gutter or another part of the building may block the ideal route.

This 15° bend creates a small change in direction while maintaining a strong upward path. A second matching bend can then return the chimney to its original direction.

As a result, installers often choose a pair of 15° bends when they only need a modest offset. The gentle angle keeps the chimney closer to vertical than a larger bend.

Key Features

• Creates a fixed 15° change in direction
• Useful for small and controlled chimney offsets
• Two-segment design provides a smooth flue path
• Maintains a continuous 125mm internal diameter
• Supports a straighter chimney route than a larger bend
• High-grade stainless-steel inner and outer casings
• Insulation helps maintain the flue-gas temperature
• Fully welded construction provides strength and durability
• Matt-black finish matches other TWPro components
• Push-fit joint supports straightforward installation
• Compatible with matching 125mm TWPro chimney parts

TWPro 125mm 15 Degree Bend Specification

• Download the TWPro Matt Black information sheet
• View the TWPro installation diagram
• Read why we recommend TWPro twin-wall flue
• Product type: fixed insulated chimney bend
• Nominal internal diameter: 125mm
• Bend angle: 15°
• Construction: two segment
• Inner casing: 0.4mm 316L-grade stainless steel
• Outer casing: 0.4mm 304-grade stainless steel
• Outer finish: high-temperature matt-black coating
• Insulation: 25mm high-density mineral wool
• Construction method: fully welded
• Joint method: push fit with locking band
• Temperature classification: T600
• Declared distance to combustible materials: 50mm
• System warranty: 25 years, subject to terms and conditions
• Paint-finish warranty: 2 years, subject to terms and conditions
• Product code: 37-125-033

Approvals and Classifications

• HETAS approved
• CE marked
• EN 1856-1 T600 N1 W V2 L50040 G50
• EN 1856-1 T200 P1 W V2 L50040 O20

The T600 designation classifies the relevant chimney arrangement for flue-gas temperatures up to 600°C. In addition, the G50 designation identifies a soot-fire-resistant arrangement with a declared distance of 50mm from combustible materials.

However, the correct classification depends on the appliance, fuel and complete chimney design. Therefore, follow the appliance instructions and TWPro installation guide.

Suitable Applications

This 125mm TWPro insulated bend may suit correctly specified heating appliances such as:

• Wood-burning stoves
• Multifuel stoves
• Compatible solid-fuel appliances
• Gas coal-effect fires
• Gas boilers
• Oil-fired boilers
• Other compatible gas and oil appliances

However, the appliance outlet size alone does not confirm the correct chimney diameter. First, check the appliance instructions. Next, confirm the required chimney classification. Finally, make sure the complete route complies with Building Regulations and TWPro installation requirements.

Creating an Offset with Two 15 Degree Bends

Installers normally create an offset by using two matching bends. The first 15° bend moves the chimney away from its original line. Then, the second bend returns it to a parallel or vertical route.

The length of pipe between the bends controls the amount of sideways movement. A longer intermediate section usually creates a greater offset.

Therefore, check the product dimensions and TWPro offset information before ordering. Also, allow for the overlap at every push-fit joint when calculating the completed chimney height.

Do not estimate the offset from the bend angle alone. The final measurement depends on the bend dimensions, intermediate pipe length and joint engagement.

15 Degree Bend or 30 Degree Bend?

Choose a 15° bend when the chimney only needs a small change in direction. Its gentle angle keeps the flue route closer to vertical and may suit small obstacles or minor alignment changes.

In contrast, a 30° bend creates more sideways movement over the same pipe length. Therefore, it may suit a larger offset where the installation allows that angle.

Before ordering, check:

• The amount of sideways offset required
• The available vertical space
• The straight pipe length between the bends
• The position of joists, rafters and other obstacles
• The appliance and TWPro installation instructions

Keep the Chimney Route as Straight as Possible

A straight vertical chimney normally provides the simplest path for combustion gases. Every bend adds some resistance and creates another area where deposits may collect.

Therefore, only add bends where the chimney needs to avoid an obstacle or make a necessary alignment change. Furthermore, keep the total number of bends within the limits stated by the appliance manufacturer, TWPro and Building Regulations.

A gentle 15° change can help maintain a more direct upward route. However, the installer must still consider the total chimney height, terminal position and expected draught.

Two-Segment Construction

This fixed bend uses two formed sections to create its 15° angle. The design provides a controlled change in direction while maintaining the 125mm internal flue route.

Fully welded seams provide strength and durability. Meanwhile, the smooth matt-black surface creates a professional appearance for visible chimney installations.

The bend does not allow angle adjustment. Therefore, do not twist, cut or reshape it to achieve a different angle.

How Twin-Wall Insulation Helps

The mineral wool layer sits between the inner flue and outer casing. This insulation helps retain heat as combustion gases travel through the bend.

Warmer flue gases can support chimney draught and help reduce condensation. In addition, the insulation lowers heat transfer to the outer casing when compared with single-wall stove pipe.

However, the bend can still become hot during use. Therefore, maintain the required clearance and prevent accidental contact where necessary.

Strong Stainless-Steel Construction

The inner casing uses corrosion-resistant 316L-grade stainless steel. This surface carries combustion gases through the chimney.

Meanwhile, the outer casing uses 304-grade stainless steel with a high-temperature matt-black coating. As a result, the bend provides durable protection and matches other TWPro black chimney components.

The combination of stainless-steel casings, insulation and fully welded seams creates a robust bend for correctly designed internal or external chimney routes.

Installation Guidance

First, confirm the required bend angle and offset dimensions. Next, inspect the bend and make sure both joint ends remain clean and undamaged.

Push each connection fully into the adjoining TWPro component. Then secure every joint with the correct locking band. Finally, check that the chimney remains aligned, stable and correctly supported.

Install each component in the direction shown in the TWPro instructions. Correct joint orientation helps keep condensate and combustion deposits inside the chimney.

Do not cut or alter the bend. Instead, select the correct bend angle and straight pipe lengths for the planned route.

Supporting a Chimney Offset

An offset creates sideways forces and adds weight to the surrounding joints. Therefore, provide suitable support above and below the directional change.

Do not rely on locking bands alone to support the chimney. Instead, use the correct TWPro wall bands, base supports, ceiling supports or roof supports.

The installer must also check the maximum distance between supports and the permitted unsupported height. Always follow the current TWPro installation guide.

Distance to Combustible Materials

Maintain at least 50mm between the TWPro insulated chimney and combustible materials for the relevant T600 G50 system arrangement.

Combustible materials can include timber, roof structures, furniture, insulation and other heat-sensitive products. Furthermore, plasterboard may form part of a timber structure and should not automatically count as non-combustible.

Measure the clearance from the nearest part of the bend’s outer casing. This check matters because an offset may move the chimney closer to nearby building materials.

Keep the required air gap clear. Do not fill it with insulation unless the manufacturer provides a tested component for that exact purpose.

Locking Bands and Joint Security

TWPro uses push-fit joints with locking bands. Push each connection fully together before closing the band around the joint.

The bend will create two joints within the chimney route. Therefore, make sure you have the correct locking band for each connection.

A locking band secures the joint but does not provide structural support. Use separate TWPro support components to carry the chimney weight and control sideways movement.

Can the Bend Pass Through a Wall or Ceiling?

Keep chimney bends and their joints visible and accessible wherever possible. Do not position a bend joint inside a wall, ceiling, floor, roof or other concealed building penetration.

Instead, use straight TWPro pipe with the correct tested sleeve, fire-stop, support or flashing component through the structure.

Plan the offset so both bend joints remain accessible for inspection. Always follow the manufacturer’s required joint positions and clearances.

Can I Mix TWPro with Another Chimney Brand?

Do not connect this bend to another manufacturer’s twin-wall chimney unless both manufacturers provide written approval.

Different chimney systems can use different outer diameters, joint depths, insulation specifications and locking methods. Therefore, parts with the same stated internal diameter may not connect safely.

Using matching TWPro components helps preserve the tested system classification and creates a secure, consistent chimney installation.

Maintenance and Chimney Sweeping

Bends can collect more soot and combustion deposits than straight vertical pipes. Therefore, the complete chimney must provide suitable access for inspection and cleaning.

Arrange chimney sweeping at intervals that suit the appliance, fuel and frequency of use. During servicing, inspect the bend, welded seams, locking bands and nearby supports.

Replace the bend if it becomes badly corroded, distorted, damaged or insecure. Furthermore, arrange a professional inspection if you notice smoke leakage, poor draught or a change in appliance performance.

Why Choose TWPro?

TWPro combines a durable 316L stainless-steel inner casing with a strong 304-grade stainless-steel outer casing. In addition, the mineral wool insulation helps retain heat and supports a stable flue temperature.

The FitSystem push-fit joint makes assembly straightforward, while locking bands secure the connections. Furthermore, the range includes matching pipes, bends, tees, supports, flashings and terminals for a complete chimney installation.

Finally, the smooth matt-black finish creates a professional appearance for modern and traditional properties.

Why Buy from SNH Tradecentre?

• Specialist stove, chimney and flue-system supplier
• Extensive range of matching 125mm TWPro components
• Practical product advice from an experienced team
• Nationwide UK delivery options
• Secure online ordering
• Trade counter in Birchington, Kent
• Support before and after your purchase

Need help calculating an offset or selecting the correct pipe lengths? Call SNH Tradecentre on 01843 842727 before ordering.

Frequently Asked Questions

What angle is this TWPro bend?

This product has a fixed angle of 15°. Model 37-125-033 identifies the TWPro 125mm two-segment 15-degree bend.

What diameter is the bend?

It has a nominal internal flue diameter of 125mm, which is approximately 5 inches.

Can I use two bends to create an offset?

Yes. Installers commonly use two matching 15° bends with a straight pipe section between them to create a gentle offset.

How do I calculate the offset?

The offset depends on the bend dimensions and the effective installed length of the pipe between the bends. Check the TWPro dimensions before ordering.

Can I adjust the bend angle?

No. This is a fixed two-segment 15° bend. Do not twist, cut or reshape it.

Is a 15-degree bend better than a 30-degree bend?

The 15° bend suits smaller offsets and keeps the chimney closer to vertical. A 30° bend creates more sideways movement over the same pipe length. Choose the angle that matches the designed route.

Can I use it with a wood-burning stove?

Yes, it may suit compatible wood-burning and multifuel appliances. However, check the required diameter and chimney specification in the appliance instructions.

How far must it remain from combustible materials?

The relevant T600 G50 system has a declared distance of 50mm from combustible materials. Measure this clearance from the closest part of the bend’s outer casing.

Can I install it inside a wall or ceiling?

Keep bend joints accessible and away from building penetrations. Use straight pipe with the correct tested components where the chimney passes through walls, ceilings, floors or roofs.

Does the offset need extra support?

Yes. An offset can place sideways forces on the chimney, so use the correct TWPro supports above and below the change in direction.

Can I connect it to another chimney brand?

Do not mix chimney brands unless both manufacturers provide written approval. Similar-looking components may use incompatible joints.

What is the product model?

The product model is 37-125-033.